Attains oftht Onenial Lapis Lazuli. 79 



precipitate which was formed and re-diflblved by excefs of acid, and afterwards formed 

 again by carbonate of pot-aQi, was diflblved again by fulphuric acid. A new precipitate of 

 filex was thus obtained, which after ignition weighed fix grains. The filex was feparated, 

 ! and pot-afli being then added, cryftals of alum were obtained. Thefe were diflblved in 

 water, and the alumine, after precipitation, drying, and ignition, weighed 29 grains. 



L. I had afcertained by a previous experiment, that all the calcareous earth contained in 

 the lapis was not faturated by the crrbonic acid, but that part was combined with the 

 fulphuric acid. I had boiled in a large quantity of water a portion of the pulverifed ftone -r 

 the water, after filtration, did not appear very tranfparent. I poured in the muriate of 

 barytas, and a precipitate was immediately formed confiding of fulphate of barytes. In 

 order to afcertain the proportion of fulphate of lime, I fuperfaturated with muriatic acid the 

 liquor which remained from the precipitate C and the water of edulcoration ; after which 

 I poured in muriate of barytes, and obtained a precipitate of fulphate of barytes, which 

 when perfedly dried weighed ig\ grains. 



I fufpefted that the alkalis made ufe of In the experiments D and E might contain a 

 fmall portion of fulphate of pot-afli, and by that means have contributed to the precipitate 

 of the fulphate of barytes. To afcertain this fa£):, I diflblved an equal quantity of alkali; and 

 having fuperfaturated it with muriatic acid, and treated it with the muriate of barytes, the 

 fulphate of barytes which fell down was carefully collefted and dried, and weighed It grain, 

 a quantity to be deduded from the foregoing, and leaves 1 8 grains of fulphate of barytes to 

 determine the proportion of the fulphate of each ; and by computation I find that 200 

 grains of the lapis contain 8.18 of fulphuric acid, of the fpeclfic gravity 1.850, or in 

 combination with calcareous earth 13 grains of fulphate of lime. This calculation is 

 founded upon my experiments, which fhew that with the difl^erence of a very fmall frac- 

 tional quantity, 100 parts of fulphuric acid of the fpeclfic gravity 1.850 form 220 of ful- 

 phate of barytes. The fame quantity of acid for its faturatlon with calcareous earth de- 

 mands either 100 parts of carbonate of lime, or 55 of pure lime, and forms 160 of fulphate 

 of lime. 



The 200 grains of lapis lazuli contain therefore as component parts : 



siliceous earth — ■<H29> — _ 02 



Ik bJ 



Calcareous earth — { I ^r } 64 but ignited — 35 



Alumine — — K 



Oxide of Iron ^ — I 



Sulphuric acid — L 



Carbonic acid — B 



Water — — A 



But 



